As a cause of global warming, the greenhouse effect due to CO2 is pointed out, and countermeasures against the same must be quickly taken internationally in saving the global environment. Various fields of human activity burning fossil fuel as generation sources of CO2, the demand for suppression of CO2 emissions is further increasing. Accordingly, for power generation facilities such as thermal power plants and the like using a large amount of fossil fuel, a method that exhaust gas from a boiler is contacted with an amine-based absorbing liquid such as an aqueous solution of amine compound so as to remove CO2 in the exhaust gas and recover the same is energetically studied.
When recovering CO2 from exhaust gas using such an absorbing liquid, a decarbonated exhaust gas from which the CO2 is recovered is accompanied by the absorbing liquid and anime compounds derived from the absorbing liquid. Additionally, in order to prevent air pollution by the amine compounds, it is necessary to reduce the discharge amount of the amine compounds which are emitted together with the decarbonated exhaust gas.
Conventionally, Patent Literature 1 discloses that plural stages of water washing portions which recover an amine compound accompanied by a decarbonated exhaust gas by bringing a washing liquid into contact with the decarbonated exhaust gas from which CO2 is absorbed and removed by a gas-liquid contact with an absorbing liquid are provided, and a recovery process of an amine compound accompanying a decarbonated exhaust gas is sequentially performed in the plural stages of the water washing portions. For the washing liquid of Patent Literature 1, condensed water obtained by condensing and separating moisture contained in CO2 in a process where CO2 is diffused from an amine-based absorbing liquid which has absorbed the CO2 so as to regenerate the amine-based absorbing liquid is used.
Further, conventionally, Patent Literature 2 discloses that a cooling portion where a decarbonated exhaust gas from which CO2 is absorbed and removed by a gas-liquid contact with an absorbing liquid is cooled, and a contact portion where condensed water which has been condensed in the cooling portion and the decarbonated exhaust gas are in counterflow contact with each other. Furthermore, Patent Literature 2 discloses that a water washing portion which recovers an amine compound accompanying a decarbonated exhaust gas by bringing a washing liquid into contact with the decarbonated exhaust gas from which CO2 is absorbed and removed by a gas-liquid contact with an absorbing liquid are provided, and for the washing liquid, condensed water which has been condensed in a cooling tower where exhaust gas before CO2 is recovered therefrom is used.